Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
In this article we provide a comparison of different formulations for hedonic regression analysis in order to construct a quality adjusted price index for the Spanish car market over the period 1981 to 2005. Specifically, we address the issue of instability of coefficients over time, and propose two alternative estimation procedures based, firstly, on a moving sample of observations and, secondly, on a moving average of estimated coefficients in single period equations. The statistical tests applied support the proposed methodologies. On empirical grounds two conclusions can be emphasized. Firstly, our study concludes that, taking quality changes into account, car prices in Spain deflated by consumer price index (CPI) declined by 40% between 1981 and 2005. This result is robust to the alternative estimation procedures employed in the study. Secondly, an analysis of σ-convergence shows that for quality adjusted prices a clear trend in σ-convergence emerges between 1986 and 1992, whereas such a trend does not exists for observed prices. This result has to be related to Spain's integration into the European Community (EC).